Rigidity tests were performed on maxillary major connectors of different designs and mandibular major connectors of the lingual bar-type with different crosssectional shapes and thicknesses. Each major connector was clamped on one side while the other side was subjected to bending, torsion, and bending under torsion forces. Deformation was measured with a micrometer microscope. The most rigid maxillary major connector was the design incorporating the anterior-posterior palatal bar. The most flexible was the U-shaped palatal bar. The full pear-shaped lingual bar (4 × 4 mm) was the most rigid of the major connectors. Among the more conventional lingual bars, the semielliptical bar (3.75 × 1.75 mm) was the most rigid, and the narrow semielliptical bar (4 × 1.5 mm) was the most flexible.